Method of manufacturing particle-based image display

ABSTRACT

A method of manufacturing a particle-based image display having a plurality of imaging cells is disclosed. The method includes filling the plurality of imaging cells with a plurality of first particles, identifying a defect associated with one or more of the imaging cells, and repairing the defect within a unit corresponding to part of the plurality of imaging cells.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing aparticle-based image display, and more particularly, to a method ofinspecting and repairing defects in the manufacturing process.

2. Description of the Related Art

Particle-based image display (PBD) technology has drawn a great deal ofattention by those skilled in display technology in recent years. Due toits wide viewing angles, low power consumption, light weight, andthinness, PBDs are widely applied in a variety of products such aselectronic readers, electronic paper, electronic tags, electronicsignage, and the like. PBDs are capable of providing visual effectswhich are similar to that of reading paper products. Different frombacklight-type flat panel displays, PBDs utilize reflected ambient lightfrom pigment particles to display content, and thus, there is no glareor other effects resulting from strong external light which affectcomfortable reading. In addition, PBDs consume power only when thedisplayed contents are subjected to change.

A PBD includes a plurality of independently addressable display unitsspatially arranged in the form of a matrix. Each display unit is formedwith a plurality of display cells, where each display cell is filledwith pigment particles. Each display unit is disposed between a pair ofopposing, spaced-apart substrates, and electrodes are disposed on atleast one substrate. By applying voltages onto the electrodes, thecharged pigment particles in the cells migrate by attraction to therespective electrodes having opposite polarities as a result of anelectric field generated between the pair of substrates. Thus, thelocations of the pigment particles can be controlled by changing thepolarities of the electrodes, thereby displaying images of the reflectedlight from the pigment particles or fluid.

In FIG. 1A to FIG. 1C, a method of manufacturing a dry powder typeparticle-based image display 100 is shown. A plurality of rib structures122 are first formed on a substrate 110 to define a plurality of imagingcells 120. A plurality of first particles 130 and second particles 140are then filled into the plurality of imaging cells 120 sequentially.After that, the plurality of imaging cells 120 are sealed with a backpanel 150 on which electrodes 160 are formed. Each imaging cell 120 isfilled with the plurality of first particles 130 and the plurality ofsecond particles 140 having different colors in contrast (e.g., blackand white) and having charges with opposite polarities, respectively.

Thus, the floating state and the falling state of the different coloredparticles 130, 140 in the imaging cells 120 are controlled by varyingexternal electric fields imposed on the pigment particles, therebyachieving color image displaying with coordination of a color filter. Inaddition, in order to overcome the slow response drawbacks ofelectrophoretic displays, the pigment particles 130, 140 in the drypowder type displays are selected to have better flowability andfloodability. As such, the pigment particles have the characteristics offluidity, and thus move fast when driven by an electric field. However,during the filling process, the pigment particles 130, 140 may bedispersed or spread all over the cells, i.e., wherein the pigmentparticles 130, 140 are not dispersed along a straight line even underthe effect of the gravity. If the pigment particles 130, 140 are notuniformly filled, the display 100 would generate color deviation incolor image displaying so that the yield rate of the display would bereduced. In addition, the black and white colored particles havingcharges with opposite polarities may easily aggregate together becauseof electrostatic attraction, which makes it difficult to fill thepigment particles into the imaging cells and affects the productionyield. Lowering the charge density of the pigment particles may reducethe electrostatic attraction generating particle aggregation; however,it will reduce the sensitivity of the pigment particles to a drivingelectric field, which results in slow responses. Otherwise, the pigmentparticles would need to be driven with high voltages. Indeed, itpresents a great challenge for the filling of the particles process touniformly fill the black and white colored particles having charges ofopposite polarities in each display cell. Thus, quality control for theuniformity of the filling of the particles plays an important role inthe fabricating process of the particle-based image display.

In the conventional manufacturing process of PBDs, most quality controlsteps are performed after sealing the plurality of imaging cells. Thus,even though defects are inspected, there is no way for repair. Forexample, U.S. Pat. No. 7,843,621 discloses a test method for use in theproduction of an electro-optic display, in which the only suggestionafter defect inspection is to record the locations of defective cells,so as to ensure that the units are not used in final products. ThoughJP200603918 discloses a method of manufacturing a particle-baseddisplay, which includes an optical defect inspection procedure beforesealing the front panel, no corresponding action is suggested to dealwith the defects.

Therefore, a heretofore unaddressed need exists in the art to addressthe aforementioned deficiencies and inadequacies.

BRIEF SUMMARY OF INVENTION

In one aspect of the present invention, a method of manufacturing aparticle-based image display having a plurality of imaging cells isdisclosed. The method includes filling the plurality of imaging cellswith a plurality of first particles, identifying a defect associatedwith one of the imaging cells, and repairing the defect within a unitcorresponding to part of the plurality of imaging cells.

According to another aspect of the present invention, a method ofmanufacturing a particle-based image display having a plurality ofimaging cells is disclosed. The method includes filling the plurality ofimaging cells with a plurality of first particles, irradiating theplurality of imaging cells with a plurality of polarized light beams,identifying one or more defects according to an intensity of a pluralityof scattered light beams scattered by the plurality of first particlescorresponding to each imaging cell, and repairing the one or moredefects by removing at least part of the plurality of first particles,by filling with another plurality of first particles, or by removingforeign matter.

In yet another aspect of the present invention, a method formanufacturing a particle-based image display is disclosed. The methodincludes providing a substrate having a plurality of imaging cells,filling a plurality of first particles into each of the plurality ofimaging cells, performing a first optical inspection to identify one ormore first units, removing the first particles in the one or more firstunits, and refilling another plurality of first particles into theplurality of imaging cells located in the one or more first units.

These and other objectives of the present invention will become apparentto those of ordinary skills in the art after having read the followingdetailed description of the preferred embodiments which are illustratedin the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, where:

FIG. 1A to FIG. 1C are schematic diagrams illustrating a conventionalmethod of manufacturing a particle-based image display;

FIG. 2 and FIG. 3 show a method of manufacturing a particle-based imagedisplay according to a first embodiment of the present invention;

FIG. 4 is a schematic diagram of an AOI device utilized in an embodimentof the present invention;

FIG. 5A is a schematic diagram of a method of defect inspectionaccording to an embodiment of the present invention;

FIGS. 5B and 5C are schematic diagrams of a method of defect repairaccording to an embodiment of the present invention;

FIG. 6 is a schematic diagram showing a height identification method toobtain the filling of the particles conditions in the plurality ofimaging cells;

FIG. 7 is a schematic diagram of a method of defect inspection for theplurality of second particles according to an embodiment of the presentinvention; and

FIG. 8 is a flow chart of a method of manufacturing a particle-basedimage display according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION

The present invention provides a method of manufacturing aparticle-based image display in which defect inspection and repair areperformed for improving the yield rate of the filling of the particlesand for reducing the manufacturing cost.

FIG. 2 shows a method of manufacturing a particle-based image displayaccording to an embodiment of the present invention. A substrate isfirst provided, and a plurality of rib structures are formed on thesubstrate to form a plurality of imaging cells in step S11. After that,the plurality of imaging cells are filled with a plurality of firstparticles having a predetermined color in step S12. In step S13, adefect inspection is then followed to identify a defect occurring in animaging cell, and a classifying step is further performed in step S14.After that, the defect associated with the imaging cell within a unitcorresponding to part of the plurality of imaging cells is repaired instep S15.

In an embodiment of the present invention, a pre-filling method is usedfor the filling of the particles. In the pre-filling method, theplurality of first particles are first filled into a template having aplurality of compartments corresponding to the plurality of imagingcells. Each compartment has a suitable containment volume which isdesigned to contain a predetermined quantity of the plurality of firstparticles. After that, the template is mounted on the substrate. Theplurality of first particles is then transferred from the plurality ofcompartments into the plurality of cells under influence of a field,such as a gravity field or an electric field.

In an embodiment of the invention, the particle filling process, thedefect inspection process, the defect repairing process and thepackaging process can be proceed as a continuous procedure. For example,as shown in FIG. 3, the particle filling apparatus 302, the defectinspecting apparatus 304, the defect repairing apparatus 306 and thepackaging apparatus 308 can be disposed in a continuous proceeding lineto perform the particle filling process, the defect inspection process,the defect repairing process and the packaging process in a continuousway.

According to the embodiment of the present invention, identifying adefect may be achieved by optically or acoustically inspecting thedefect. In an embodiment of the present invention, identifying thedefect is performed optically by an automatic optical inspection (AOI)machine. Referring to FIG. 4, an automatic optical inspection machine400 is shown, which comprises an inspecting module 402 used forinspecting a defect of a particle-based image display and a laserrepairing module 404 used for repairing the defect to increase yield ofthe display. Taiwan patent M317023 is incorporated herein by reference.In an embodiment of the invention, the repairing module can repair thedefect by automatic mode or manual mode.

It is known that ultrasonic transducers can be used to generate highfrequency sound waves. The distance to an object is determined bycalculating a travel time between the sending of a signal and receivingof an echo. Therefore, a change in the travel time of ultrasonic wavesassociated with separate imaging cells relates to the variation of thefilling volume of the particles in the plurality of imaging cells. Themeasured amplitude profile of the reflected echo at the interfacebetween the particles and the transducer can be used to inspect theadequacy of the filling process. The variation of the ultrasonicattenuation coefficient in the particles filled may also relate to theporosity of particles in a given imaging cell. To reduce measurementdistortion, however, the level of the particles accumulated ispreferably flattened by, for example, a vibrator which is operablyconnected to the substrate.

Referring to FIG. 5A, in an embodiment of the present invention,identifying a defect S13 is performed by irradiating the plurality ofimaging cells with a plurality of polarized light beams 502. When theplurality of polarized light beams 502 pass through the plurality ofimaging cells 504, part of the plurality of polarized light beams 502are scattered by the plurality of first particles 506 to form aplurality of scattered light beams. Therefore, the light 508 passing theimaging cells 504 comprises partial polarized light and partialscattering light. In an embodiment, a suitable filter 510 is utilized tobypass the plurality of polarized light beams, wherein only scatteredlight beams 514 can pass the filter 510. An optical receiver 512 is usedto receive the plurality of scattered light beams 514. The plurality ofscattered light beams 514 are received and analyzed to identify one ormore defects according to the intensity of the scattered light beamscorresponding to each imaging cell.

Distribution of the plurality of first particles 506 in each imagingcell 504 can be obtained via the intensity of the scattered light beams514 of each imaging cell 504. For example, when an imaging cell isoverfilled with particles, it is difficult for the polarized light beamsto pass through the plurality of first particles, leading to arelatively low intensity of scattered light beams when compared withthose filled with a proper dosage. In the case of an insufficient amountof particles, most of the polarized light beams pass directly throughwithout being scattered. This causes a relatively low intensity ofscattered light beams. In other words, a suitable criterion can be madeto screen defects out. In an embodiment of the present invention, athreshold value and a tolerance of the intensity are predeterminedaccording to product requirement to identify defects.

If the method using the polarized light to irritate particles in theplurality of imaging cells of the display with a filter to bypass thepolarized light is not applied, all the image cells except for thosecontained within the light spot are identified as black areas since thelight spot presents much higher intensity. Thus, it is difficult tocompare light intensity and contrast between imaging cells. On thecontrary, the analyzing method of the embodiment of invention whichinspects scattering light with polarized light being bypassed can moreclearly identify the intensity of contrast between imaging cells toestimate the filling result of the particles in imaging cells.

In an embodiment of the present invention, the method further comprisesflattening the plurality of first particles before identifying thedefect. For example, a vibration mechanism such as supersonic/ultrasonicgenerator may be used to further disperse potential aggregations of theplurality of first particles so as to improve the reliability of defectinspection. In particular, the supersonic/ultrasonic mechanism may beused to provide momentary vibrations such that the plurality of firstparticles are flattened to facilitate the process of defect inspection.

In addition, if a pre-filling process is utilized in step S12, defectinspection and repair can be also performed in a similar way mentionedabove to control a uniformity of the plurality of first particlesdistributed among the compartments of the template, thereby improvingthe uniform filling result of the particles.

Referring to FIG. 5B, an exemplary inspecting result is shown. Theintensity of scattered light beams of each cell is represented by acorresponding gray level to identify defects. According to theinspecting result, a defect analysis is then performed for classifyingthe defect into a corresponding defect type, such as insufficientfilling of the plurality of first particles, overfill of the pluralityof first particles, mura, occurrence of a foreign matter, occurrence ofimpurities or deformation of rib structures. As shown in FIG. 5B,defects in the three defective imaging cells 520 a, 520 b, and 520 c arefound among the plurality of imaging cells 511. A corresponding actionmay be taken to repair the defects. In an embodiment of the presentinvention, repairing the defect comprises removing at least part of theplurality of first particles, filling with another plurality of firstparticles, or removing a foreign matter or impurities. In an embodimentof the present invention, the plurality of first particles or foreignmatter or impurities can be performed by a method such as vacuumsuction, air blowing, voltage driving, or statistic driving.

In addition, if the repair is not efficient for some specific defecttypes, such as defective rib structures, the associated imaging cellsare marked to avoid proceeding to a subsequent process. For example, arework process may be performed for a substrate having defective ribstructures instead of a repair process.

According to the present invention, the defects are preferably repairedon the basis of one or more units. Each unit is comprised of one or moreadjoining imaging cells and has a predetermined unit corresponding topart of the plurality of imaging cells. The units in the presentinvention may have different sizes or shapes to meet fabrication processrequirements. For example, the unit 530 a is comprised four adjoiningimaging cells and the unit 530 b is comprised of six adjoining imagingcells. In an embodiment of the present invention, the AOI machinefurther comprises a computing module to determine a location of eachunit according to the result of the defective imaging cells distributionto facilitate the repairing process.

In an embodiment of the present invention, the AOI machine furthercomprises a repair module which can be moved onto a selected unit forrepairing the plurality of imaging cells within the selected unitwithout influencing the other imaging cells outside of the selectedunit. In addition, suitable equipment may be used optionally to furtherprotect the plurality of imaging cells outside of the selected unit.Referring to FIG. 5C, a mask 580 having an opening 590 corresponding tothe unit 530 a or 530 b is utilized in the process of repairing thedefects according to an embodiment of the present invention. The mask580 is first mounted on the front panel to cover all imaging cellsexcept for the plurality of imaging cells in the unit 530 a. After thedefects within the unit 530 a are repaired, the mask 580 is then movedto expose the unit 530 b for repairing the defects within the unit 530b. After the repairing process is completed, another defect inspectionmay be carried out for confirming the repair result of the plurality ofimaging cells within each unit.

The invention is not limited to the optical method to inspect thefilling result of the particles in the plurality of imaging cells.Referring to FIG. 6, an embodiment of the invention can further use anintensity identifying method to obtain the filling result of theparticles conditions in the plurality of imaging cells. As shown in FIG.6, when the stack heights of the particles in the first cell 602 and thesecond cell 604 are different, the light presents different inletangles, and the method can use image capture devices 606, 608, such as aCCD, to identify the difference to estimate the filling result of theparticles conditions in the cells. Furthermore, the invention can alsomeasure capacitance or inductance of the stack of particles filled inthe plurality of imaging cells to estimate the filling result of theparticles conditions.

After the defect inspection and repair of the plurality of firstparticles, the plurality of imaging cells are then filled with aplurality of second particles. Next, defect inspection and repair of theplurality of second particles can be carried out in a similar way toidentify another defect associated with another imaging cell and torepair the another defect associated with the another imaging cellwithin another unit corresponding to part of the plurality of imagingcells.

It is noted that the plurality of first particles and the plurality ofsecond particles tend to aggregate with each other. Thus, arearrangement of the plurality of first particles and the plurality ofsecond particles can be performed to improve the defect inspection afterthe plurality of second particles are filled in the plurality of imagingcells.

Referring to FIG. 7 an exemplary embodiment of the rearrangement of theplurality of first particles and second particles is shown. In thisembodiment, a transparent plate 701 with an electrode 703 formed thereonis used to cover the plurality of imaging cells temporarily. An externalelectric field is then applied thereon. Due to the different chargepolarities, the plurality of first particles 702 and second particles704 are driven toward different directions. As shown in FIG. 7, theplurality of first particles 702 which are black and have positivecharge polarity are driven downward, and the plurality of secondparticles 704 which are white and have negative charge polarity aredriven upward.

After that, an optical defect inspection for the plurality of secondparticles is carried out by irradiating a plurality of light beams 706to the plurality of imaging cells through the transparent plate 701. Theplurality of light beams 706 are reflected by the plurality of secondparticles 704 and then received by an optical receiver 708. Again, adefect analysis is performed according to the intensity of the pluralityof reflected light beams for classifying defects into different defecttypes. Then, the defects can be repaired in a similar way as describedabove.

In addition, another inspection may be followed to confirm the repair.If the repair is satisfactory, the plurality of imaging cells are sealedand then combined with a back panel to form a particle-based imagedisplay.

Referring to FIG. 8, a method of manufacturing a particle-based imagedisplay according to a second embodiment of the present invention isshown. First, as shown in the step S81, a substrate is provided and aplurality of imaging cells is formed on the substrate. Next, as shown inthe step S82, a plurality of first particles are filled into each of theplurality of imaging cells. As shown in the step S83, a first opticalinspection identifies one or more first unit. As aforementioned,polarized light beams and an AOI machine can be utilized to perform thefirst optical inspection. Each first unit has a predetermined number ofadjoining imaging cells and comprises at least one first defective cell.As shown in the step S84, a defect analysis is then performed forclassifying the defect into a corresponding defect type, such asinsufficient filling of the plurality of first particles, overfill ofthe plurality of first particles, mura, occurrence of a foreign matter,occurrence of impurities or deformation of rib structures. As shown inthe step S85, a first repairing is performed by removing the pluralityof first particles in the one or more first units and by refillinganother plurality of first particles into the plurality of imaging cellslocated in the one or more first units.

After that, as shown in the step S86, a plurality of second typeparticles are filled into each of the plurality of imaging cellssubsequent to refilling with the another plurality of first typeparticles. As shown in the step S87, a second optical inspection is thenperformed to identify one or more second units. Each second unit has apredetermined number of adjoining imaging cells and comprises at leastone second defective imaging cells. As shown in the step S88, a secondrepair is performed by removing the first type and second type particlesin the second units and by refilling a plurality of first and secondtype particles into the plurality of imaging cells located within theone or more second units. As shown in the step S89, the plurality ofimaging cells are sealed and then combined with a back panel to form aparticle-based image display.

According to the present invention, one or more defects may bepreferably identified before sealing the plurality of imaging cells andthese defects may be repaired on a unit-by-unit basis in accordance withthe defect types. According to the present invention, the degree ofuniformity in the filling of the particles, which is a bottleneck inmanufacturing particle-based image displays, can be improved, therebyeffectively increasing the production yield and reducing costs.

While the present invention has been described by way of example and interms of the preferred embodiments, it is to be understood that thepresent invention is not limited to the disclosed embodiments. It isintended to cover various modifications and similar arrangements.Therefore, the scope of the appended claims should be accorded thebroadest interpretation so as to encompass all such modifications andsimilar arrangements.

What is claimed is:
 1. A method for manufacturing a particle-based imagedisplay having a plurality of imaging cells, comprising: filling theplurality of imaging cells with a plurality of first particles;irradiating the plurality of imaging cells with a plurality of polarizedlight beams such that part of the plurality of polarized light beams arescattered by the plurality of first particles to form a plurality ofscattered light beams; identifying one or more defects according to anintensity of the scattered light beams corresponding to each imagingcell; and repairing the one or more defects by removing at least part ofthe plurality of first particles, by filling with another plurality offirst particles, or by removing foreign matter.
 2. The method of claim1, further comprising bypassing the plurality of polarized light beams.3. A method for manufacturing a particle-based image display,comprising: providing a substrate having a plurality of imaging cells;filling a plurality of first particles into each of the plurality ofimaging cells; performing a first optical inspection to identify one ormore first units, wherein each first unit has a predetermined number ofadjoining imaging cells and comprises at least one first defectiveimaging cell; removing the first particles in the one or more firstunits; and refilling the plurality of imaging cells located in the oneor more first units with another plurality of first particles.
 4. Themethod of claim 3 further comprising: filling each of the plurality ofimaging cells with a plurality of second particles sequent to refillingwith the another plurality of first particles; performing a secondoptical inspection to identify one or more second units, wherein eachsecond unit has a predetermined number of adjoining imaging cells andcomprises at least one second defective imaging cell; removing the firstand second particles in the second units; and refilling the plurality ofimaging cells located within the one or more second units with aplurality of first and second particles.
 5. The method of claim 3wherein performing the first optical inspection comprises: irradiating aplurality of polarized light beams toward each of the plurality ofimaging cells respectively, wherein part of the polarized light beamsare scattered by the plurality of first particles in each of theplurality of imaging cells so as to form a plurality of scattered lightbeams; and identifying the first defective imaging cells according to anintensity of the scattered light beams corresponding to each of theplurality of imaging cells.